Properties of LBO Single Crystal

Lithium triborate crystal, known as LBO (LiB3O5), is one of the best nonlinear optical crystals.

Its high damage threshold makes LBO crystals very suitable for harmonic generations of high-intensity laser radiation in a wide spectra. LBO
can get the highly efficient SHG of nanosecond, picosecond, CW and diode pumped Nd:YAG and Nd:YLF laser systems for R&D,
medical, industrial and military applications.

In addition to high damage threshold, the superiority of LBO is also proven by the SHG of Ti:Sapphire, Cr:LiSAF and Alexandrite laser
systems, as well as the optical parametric amplifiers and oscillators pumped by Excimer laser systems or harmonics of Nd:YAG systems.

With its good transmittance in the UV, LBO can achieve the tunable UV and VUV radiations by SFG.

Applications:

Frequency Conversion for Nd Laser Systems:

LBO is able to achieve phase matching for the SHG and THG of Nd:YAG and Nd:YLF lasers, using either type I or type II interaction. For
the SHG at room temperature, type I phase matching can be reached, and has the maximum effective SHG coefficient in the principal XY
and XZ planes in a wide wavelength range from 551 nm to about 3000nm. The effective SHG coefficients are as following:deff(I, XY place)
= d32cosf; deff(I, in XZ plane) = d31cos2q + d32sin2q.

The VUV output at 187.7 nm is obtained by sum-frequency generation. 2mJ/pulse diffraction-limited beam at 355nm is obtained by intra-cavity frequency tripling a Q-switched Nd:YAG laser.

The phase matching angle for Nd:YAG laser system at maximum deff under room temperature is as following: q=11.4°
and f=0° for Type I, q=90° and f=69.1° for Type II.

Non-Critical Phase-Matching Applications:

Non-Critical Phase-Matching (NCPM) of LBO is characterized by no walk-off effect, very wide acceptance angle and maximum effective coefficient. It
helps LBO work in its optimal conditions. SHG conversion efficiencies of more than 70% for pulsed and 30% for cw Nd:YAG lasers have been
obtained with good output stability and beam quality.

Properties of type I NCPM SHG at 1064nm

NCPM Temperature

148°C

Acceptance Angle

52 mrad-cm1/2

Walk-off Angle

0

Temperature Bandwidth

4°C-cm

Effective SHG Coefficient

2.69d36(KDP)

Both type I and type II non-critical phase matching can be achieved along x-axis and z-axis at room temperature, respectively. LBO
can reach both temperature NCPM and spectral NCPM (very wide spectral bandwidth) at 1300nm. This is favorable to the SHG of Nd lasers
working at 1300nm for red light output.

LBO for OPA, OPO Applications:

LBO is an excellent NLO crystal for OPOs and OPAs with a widely tunable wavelength range and high powers. Both OPO and OPA, pumped
by the SHG and THG of Nd:YAG laser and XeCl excimer laser at 308nm, have been reported. The unique properties of both type I and type
II phase matching, along with the NCPM, leave room for both research and industry.

A rather high overall conversion efficiency and 540-1030nm tunable wavelength range were obtained with OPO pumped at 355nm.

Type I OPA pumped at 355nm with the pump-to-signal energy conversion efficiency of 30% has been reported.

Type II NCPM OPO pumped by a XeC1 excimer laser at 308nm has achieved 16.5% conversion efficiency, and moderate tunable wavelength ranges
can be obtained with different pumping sources and temperature tuning.

By using the NCPM technique, type I OPA pumped by the SHG of a Nd:YAG laser at 532nm was also observed to cover a wide tunable range from
750nm to 1800nm by temperature tuning from 106.5°C to 148.5°C.

Pumped by a 4.8mJ, 30ps laser at 354.7nm, a narrow linewidth (0.15nm) and high pump-to-signal energy conversion efficiency (32.7%) were observed
by using LBO with type II NCPM as an optical parametric generator (OPG) and BBO with type I critical phase matching as an OPA. By
increasing the temperature of LBO and rotating BBO, we can obtain laser radiation from 415.9nm to 482.6nm.

The calculated results and tuning curves of both type I and type II OPO of LBO pumped by the SHG, THG and 4HG of Nd:YAG laser are available
upon request.